1. Field of the Invention
The invention relates to a heat-transfer type printer for winding a ribbon while printing is being performed and, more particularly, to a printer capable of reducing the consumption of a ribbon at a printing completion section.
2. Description of the Related Art
A conventional line-print type printer for winding or taking up a ribbon while a printing process is being executed will be described below with reference to FIG. 7. The printer causes a platen 53 to feed recording paper 51 upon printing and rotates a ribbon roll 57 so as to convey a ribbon 55 in synchronism with a feed speed of the recording paper 51. Further, the printer heats a heating element of a thermal head 22 for carrying out the printing in the form of a line so as to dissolve heat-soluble ink on the ribbon 55, thereby transferring it onto the recording paper 51. The printer feeds the ribbon 55 subjected to the heat transfer by a distance X corresponding to a time interval determined by characteristics of the heat-soluble ink in a state in which the thermal head 22 remains in a pressed condition (i.e., in a state in which the recording paper 51 and the ribbon 55 are brought into contact with each other not so as to be separated from each other), thereby fixing printing characters onto the recording paper 51. That is, it is necessary to use up or consume the ribbon 55 by the distance X without releasing the thermal head 22 after the printing has been carried out by the thermal head 22. The consumption of the ribbon 55 by the distance X is inevitable to improve the quality of the printing.
A so-called white-line skip operation executed by a printer such as used in a facsimile apparatus or the like will next be described with reference to FIGS. 8(A) and 8(B).
In the facsimile apparatus, even if a null or blank area or portion is formed on the recording paper 51 from a line 51A when the printing is being performed in line form as shown in FIG. 8(A), the recording paper 51 and a ribbon 55 are continuously fed in directions indicated by arrows Y1 and Y2, respectively. When the length of the blank portion existing under printing reaches a predetermined length A, the feeding of the recording paper 51 and the ribbon 55 is stopped so as to wait for the following printing. That is, the following printing is placed in a waiting state in a condition in which the ribbon 55 has been consumed by the length A. FIG. 8(B) shows the manner in which the recording paper 51 shown in FIG. 8(A) is viewed in a direction indicated by an arrow Y3. In FIG. 8(B), the printing is made to a shadowed area or portion above the line 51A, whereas the printing is not made to an area or portion below the line 51A due to the white line skip.
Further, a process effected in the case where the following print data is not input during standby in the above condition and a page end has been detected, will be described with reference to FIGS. 9(A), 9(B) and 9(C).
In the conventional facsimile apparatus as described above, when all the white lines free from the printing are detected, a white line skip is started so that each of a recording paper 51 and a ribbon 55 is fed by the predetermined length A and a process for starting the following printing is placed in a waiting state. When a page end is detected during its waiting state, the ribbon 55 is fed by the aforementioned distance X required to determine or fix the printing without any condition as shown in FIG. 9(A). Next, a thermal head 22 is released as shown in FIG. 9(B). Thereafter, the recording paper 51 is ejected or discharged as shown in FIG. 9(C). Therefore, when the printing is completed after the ribbon 55 has been fed by a distance corresponding to an A lines in accordance with the white line skip, the total length of A+X is consumed.
In order to reduce the consumption of an ink ribbon, U.S. Pat. No. 4,709,242 discloses a device in which a printhead is released from the platen every time blank (space) data is transferred to be printed. However, in such a device, the control for effecting up-and-down movement of the print head is very complicated. Likewise, there is a tendency to smudge or place ink on the recording medium when the printhead is returned to contact the ink ribbon next to the recording medium.